Feline Calicivirus

Introduction

The normal hosts for this virus are domestic cats and cheetahs. The virus has a high morbidity/low mortality rate, but affected animals can be further compromised by concurrent infection. The incubation period is 2-10 days.

Clinical signs include:

• Vesicles and ulcers of the oral epithelium (2-5mm)
• Nasal and ocular discharge
• Sneezing
• Anorexia

Variable signs include:

• Pyrexia
• Dyspnoea
• Conjunctivitis
• Rhinitis
• Tracheitis
• Pneumonia

Differential Diagnoses may include:

• Feline Herpes
• Clamydophila felis
• Bordetella bronchiseptica

Recovery can be followed by carrier status

Epidemiology

FCV is endemic worldwide. Transmission occurs through direct contact with secretions of carrier cats or indirect contact via drinking bowls, etc. Clinical disease is most frequently seen in kittens; active immunity is generally present in animals over 1 year of age. Antigenic variation means that subclinical reinfections can occur.

Antigenicity

A single serotype has been identified which typically has antigenic variations.

Recent strains of the virus have been shown to cause systemic disease, where the initial upper respiratory signs are followed by:

• Severe pyrexia
• Oedema, particularly of the head and limbs
• Skin ulcers
• Icterus and Petchiae

The mortality rate of recently emerging strains can be as high as 50%, and higher in cats over 1 year of age. Conventional vaccination are thought to be ineffective against these strains.

Diagnosis

Clinical signs are non specific with many other differentials. Nasal, conjunctival, or oropharyngeal swabs can be taken for virus isolation.

• Diagnosed by pyknosis (an irreversible condensation of chromatin in the cell nucleus undergoing necrosis or apoptosis) - Feline herpes causes cellular swelling and syncytia.

Control

Virulent isolate outbreak:

• Quarantine and restrict movement

Prevention:

• Vaccination:
  • Live or dead vaccines available
  • Contain broadly cross-reactive strains
  • In combination with feline herpes and panleukopenia virus
  • Live nose-drop vaccine now available in US
  • Particular concern for catteries

• Rhinitis,
• Suggested in the presence of ulceration of the dorsal and lateral edges of the tongue, hard palate and external nares
• Lesions present may include interstitial pneumonia with necrotising bronchiolitis
• Also see Feline viral rhinotracheitis above